The present invention relates to a retraction mechanism for an emergency locking seat belt retractor and more specifically to a mechanism capable of selectively applying one of two different magnitudes of spool rewind bias force to the safety belt retractor spool.
Various types of dual tension safety belt retractor mechanisms have been employed and are shown in the prior art for selectively applying a main spring rewind bias to the safety belt spool during normal belt extraction and retraction relative to the retractor and for applying a lower tension to the belt while the safety belt is in use about the vehicle occupant.
Exemplary of prior art, dual tension retraction mechanisms are those disclosed in U.S. Pat. No. 4,165,844 which utilizes a main rewind spring which is blocked out or locked to the retractor housing when the belt is in its low tension mode. The unlocking or locking of the main spring for power retraction of the belt is accomplished by a partial rewinding of the belt reel under the low tension bias. U.S. Pat. No. 4,346,858 provides another dual tension safety belt retractor which does not require the partial rewinding of the belt reel. In this mechanism a pawl is mounted to a pawl carrier which upon coupling to a coacting ratchet wheel blocks out the force of the main rewind spring. This patent also includes means for unlocking the power rewind spring while the pawl is engaged with the ratchet and is accomplished by a release arm which disengages the pawl. The release arm is moved by an activation mechanism such as a manual switch, solenoid or air/vacuum pressure valves.
It is an object of the present invention to provide a retractor having a dual tension mode of operation.
Accordingly, the invention comprises a dual tension safety belt retracting device comprising: a frame, a spool rotatably mounted on the frame, for storing safety belt webbing. The device including first and second ratchet wheels and an outer tube, extending through and connecting the first and second ratchet wheels, wherein an end of the outer tube extends beyond the first ratchet wheel. An inner shaft extends through and is rotatably disposed in the outer tube; a main, high torque rewind spring is provided to apply a rewind bias to the inner shaft. A low torque, rewind spring connects the outer tube to a control ratchet wheel; a cap interconnects the control ratchet wheel to the inner shaft. A control pawl means for engaging the control ratchet wheel, is rotatably mounted relative to the frame, and movable between a first position disengaged from the control ratchet wheel and a second position in engagement with the control ratchet wheel wherein when the control pawl means is in its second position, it is effective to block out the main rewind spring from exerting a bias on the safety belt webbing. The device further includes means for causing the control pawl means to move between the first and second position. In one embodiment of the invention such means includes a follower movable in response to the amount of webbing rewound on a designated spool. In other embodiments a solenoid and cable are used. In the preferred embodiment of the invention a second spool is also mounted to the frame and webbing engaging means such as the follower extends to and senses the amount of webbing on the second retractor thereby moving the webbing engaging means and hence moving the control pawl means between the first and second positions.